The present technology relates to a flow channel device, a particle sorting apparatus, a particle outflow method, and a particle sorting method for circulating particles such as cells.
As apparatuses that sort particles such as cells, a fluorescence flow cytometer and a cell sorter are known. In those apparatuses, under an appropriate vibration condition (generally, an exit flow velocity of several m/s and a vibration count of tens of kHz), cells are closed in a gas-liquid interface at an ejection opening by a fluid, and charges are given to the cells at the same time. The cells fly as droplets in a direction in accordance with a charge quantity in air to which a static electric field is applied and are eventually sorted into a sorting container provided outside a flow channel.
The technology is useful in the case where the flow velocity is relatively high as described above. For a flow cytometer for a low flow velocity or a dielectric cytometer, it is difficult to make droplets and satisfy an ejection condition for the droplets. In view of this, it is desirable to perform a sorting operation in a flow channel having branches and hold cells on a rear stage.
As a sorting mechanism in the flow channel, a method for changing a flow direction of a fluid by using a piezoelectric element or the like and indirectly driving cells in the fluid has been proposed. However, the responsiveness of the mechanical element is an approximately millisecond. In consideration of the responsiveness of a pressure wave of the flow channel, a sorting speed for the cells has a limitation.
On the other hand, as a method for directly driving the cells, a dielectrophoresis method has been proposed. Japanese Patent Translation Publication No. 2003-507739 discloses that a difference of a dielectrophoretic force between cell types and a difference of a sedimentation rate therebetween are used, thereby separating cells by type which flow in a flow channel in which an electrode is provided. Further, Japanese Patent Application Laid-open No. 2012-98075 discloses a cell sorting method by which cells that flow in a flow channel are analyzed to determine whether the cells are targets to be sorted or not, and in accordance with a sorting signal transmitted on the basis of the determination result, an electric field is applied. By the method, it is possible to sort the cells as the sorting targets by a sufficient dielectrophoretic force.